Electric furnace



July 21, 1925.

A. RUCKSTAHL ELECTRIC FURNACE Filed May 11,

Patented July 21, 1925.

PATENT OFFICE.'

ALFRED BUCKSTAHI, OF DETROIT, HJIJHIGAN',A ASSIGNOR TO HOLCBOFT GO., 0F

. DETROIT, IICBIGAH, A CORPORATION OF MICHIGAN.

` marc nummer.

Appunti 1aed-ny 11, 1922. seran no. 560,187.

To all 'whom z't may concern:

Be it known that I, Amman RUCKsrAHI., a citizen of the United States of America, residing at Detroit, in the county of Wayne and Stateof Michigan, have invented certain new and useful Improvements in Electric Furnaces, of which the following is a specification, reference being had therein to the accompanying dra This invention relates to electric furnaces especially designed for the heat treatment of relatively small objects at high temperatures.

It has for its object to provide an arrangement of electric resistance elements in which variations of temperature may readily be made without the removal or alteration of parts and in -which the resistor unit is readil removable to 'permit the substitution t erefor of interchangeable units having different heat characteristics wherebygreat variations in temperature may be obi tained with a minimum lo of time.

vA further object of the invention is to provide a form of electric resistance unit, 1n which insulating means is provided for the electric resistance element or elements, the insulating means consisting of a refractorysubstance provided with a framework consisting of a me c alloy highly' resistant to heat and oxidation whereby a rigid metallicstruture will prevent or lessen the likelihood of fracture of lthe refractory elements so that in theopera tion of inserting and removing the resistor units the danger of breakage will be reduced 'to a Other objects will appear in connection with the description, reference being had to the accompanying drawing, in'which- Figure 1 is a longitudinal section through a furnace shown more or le diagram- Fig. 2 is a section therethrough;

Fig. 3 is `a fragmentary detail showing y. the manner in which a resistance 'element is secured within the refractory insulating member, and

' FigA is a diagram showing a typical wiring system.' .Y Y

The furnace will consist of suitable insulating wall 1 sufro an inner chamber 2 provided withpdg-actory 1ining 3 having a doorway 4 which may be provided with -any suitable closure (not shown). Within the chamber 2 a iloor is mounted, the ioor 'preferably being of a metallic alloy highly resistant to heat and oxidation.

Through the side wall of the furnace and through the refracto lining, openings 6 and 7 are formed, sai openings being provided with closures 8 and 9 of any suitable material. The openings are of 'a size -to permit the ready Vinsertion and removal therethrough -of the resistor elements 10. These elements consist of side bars 11 which may be of the configuration shown in cross section lin Fig. 1, the vertical flanges of these metallic elements being formed4 at intervals with webs 12 arranged in pairs to receive therebetween transverse bars 13 of 'a refractory material such as alundum. 'The members, 11 may be connected preferably near each end by transverse strips 1 4 preferably of the same alloy as that used for themembers 11, the .strips-14; being welded or otherwise secured to side members 11 to form a ri 'd frame'.V

. The re ctory insulating -members `13 have a series of perforations lfvthrough which extend the electric resistance coils 16. These coils are preferably arranged as shown diagrammatically in Fig. 4. The,

perforations 15l as indicated in Fig. 1 are one of the insulator bar 13, and an element 16 paging through one of the perforations'in the end bar, is bent upon itself as indicated at 17 and returned through the ad- "ant hole in the same horizontal plane.

uch a coil will thus extend in substantially hairpin-'shape from one end of. the framework to the other as indicated in Fig. 2, and' all of the looped resistance members in each horizontal plane will preferably be arranged arragi at three different distances from' By throwing the appropriate switches 18,

19 or 20 the resistor elements in any plane may be thrown into circuit so that any series or any combination of series may used without interference with those not 1n the circuit. As shown; in Fig. 1, the heating elements will be arranged above and below the floor so that heat may be supplied to the chamber 2 in 'the embodiment herein illustrated by many different combinations of heating elements, thus permitting considerable variation of heat conditions and temperatures withoutremoval of the heating units. n

To obtain other heating conditions it will merely be necessary lto remove the closure members 8 or 9 whereupon one of the ele- Y nientsniay be withdrawn through the opentics.

desired."

ing 6 or 7 and another element substituted therefor vhaving different heat characteris- The closure will then be replaced and the furnace will again be 'ready tion. Additional insulating ymeans 2]. and 22 maybe placed u on the outer wall of the furnacel opposite t e openings 6 and 7 if Certain details of the present invention are `also-described in my co-pending application, Serial No. 560,186 filed concurrently herewith. It will be obvious that many changes and modifications may be made in the details of' the structure herein illustrated without departing from the principle of my invention. The invention is therefore claimedin an o f its forms or modifications within the leclaims. l

I claim:

1. A removable heating unit for an. elecunder temperature values usable in the heat treatmentof metallic objects, said element comprising a 'supporting framework of a heat-resisting and substantially non-oxidizing alloy, refractory insulating members carried by said framework, and t. plurality of" electric resistance .elements supported by said insulating members.

2. A structure as l1n claiml, in which the electricresistance members are adapted for independent removal from, and insertion `.into thel refractory' insulating members 3. structure as in claim 1, in which the Y refractory insulating members are provided with spaced series .of perforations arranged at different distances from .their edges whereby when the electric resistance members are in place within t-he perforationsfthere are formed a plurality of layers of heating elements in different planes, the arrangement being such that the heating elements in-each plane may be independently brought-into an electric circuit.

4. As a means for producing variable heat conditions within an electric furnace operated at high tem erature usable in the heat treatment of meta lic objects, a chamber having a surrounding wall adapted for the supfor opera- Irality of independent electric vresistance ment of metallic objects, said element comgitimate and valid scope of the appended'.

tric furnace wherein the furnace is operative port of said heating units, said wall having a series of openings therethrough adapted for the insertion and removal of heating elements, and a series of interchangeable electric units of different heating characteristic adapted for insertion through said openings,

fractory members' in position, and a plu-- members carried by said insulating members.

6. A heating element for an electric furnace wherein ,the furnace is operative under temperature values usable inthe heat treaty prising a supporting lframework carrying transverse refractory insulating members, said insulating members being provided with aplurality Aof perforations, and aplurality of electric resistance members threaded' through said perforations. 7. A' heat-ing' element for an'electric furnace wherein the furnace is operative under temperature values usable in the heat treatv ment of metallic objects, said element com-" prising an open metallic framework of. an alloy highly resistant to heat and oXidation,. said framework being provided with .webs on opposite sidestliereof, refractory insulating members in engagement with said webs 105- 'and extendingacross the open framework,

said refractoryl insulating members having a plurality of perforations arranged at substantially equal intervals throughout their length,and a plurality of electric resistance 110 members passing through the perforations in said insulating members forming a series of substantially parallel runs longitudinallyv of .the heating element.

8.l A structure' as in claim 7, wherein the 115 electric resistance elements. and their terminals are connected in aplurality lofgroups,

each group being adapted for independent A connection with an electric circuit.' In "testimony whereof I aliix my signaturel l 1n presence -of two witnesses.

ALFRED RUCKSTAI-IL Witnessesr Cms. W. STAUFFIGER. 

